This was interesting - some lessons (re)learned about using micro benchmarks and how producer linger and batching work - I wrote a quick and nasty article here https://www.linkedin.com/pulse/increased-lingering-apache-kafka-40-can-increase-latency-paul-brebner-z7qlc/
Regards, Paul From: Daniel Germon <daniel.ger...@lmax.com.INVALID> Date: Saturday, 23 August 2025 at 2:27 am To: users@kafka.apache.org <users@kafka.apache.org> Subject: Re: Re: Increased latency when upgrading brokers to V4.0.0? [You don't often get email from daniel.ger...@lmax.com.invalid. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ] EXTERNAL EMAIL - USE CAUTION when clicking links or attachments Hi Sean, Thank you for the suggestion, reducing the linger to zero has indeed removed all the differences in latencies between the two versions! I managed to skim over that bit of the release notes so will have a deeper look into the KIP to see if there's anything else that could be tuned. Thanks again, Dan This message and its attachments are confidential, may not be disclosed or used by any person other than the addressee and are intended only for the named recipient(s). If you are not the intended recipient, please notify the sender immediately and delete any copies of this message. LMAX Group is the holding company of LMAX Exchange, LMAX Global and LMAX Digital. Our registered address is Yellow Building, 1A Nicholas Road, London W11 4AN.
